I used to have bad general anxiety but it turned out I had too much oxygen in me that caused me to feel more suffocated. I just breathe out longer than I breathe in. It helps get back to balance. Basically:
1. Breathe in for 6 seconds
2. Hold it
3. Breathe out for 8 seconds
4. Hold it
5. Repeat as necessary until your calm as the everglades
Get that fucking carbon dioxide out of your system